Honing element



Nov. 3, 1964 D. K. GREENBERG ETAL HONING ELEMENT 2.Sheets-Sheet 1 Filed Aug. 6, 1963 L/ l muil,

32 24 z5 n "In Nov. 3, 1964 D. K. GREENBERG ETAL 3,154,893

HONING ELEMENT Filed Aug. 6, 1955 2 Sheets-Sheet 2 a Ju'orL UJF @WW @47 Upa?,

United States Patent O 3,154,393 HNING ELEMENT Donald K. Greenberg, Rockford, and Kenneth H. Casson,

Winnebago, lil., assignors to Barnes Drill Co., Rockford, Ill., a corporation of Illinois Filed Aug. 6, 1963, Ser. No. 366,494 9 Claims. (Cl. 51-204) This invention relates to a honing element of the type in which the abrasive stick is secured in a shell or casing of molded plastic material which covers the ends, the bottom and at least part of the back or trailing side of the stick and which wears away with the working face of the stick during a honing operation. In elements of this type the plastic is usually extended beyond the ends of the abrasive stick in the form of blocks presenting rounded end surfaces which fit snugly into the ends of the slot of the honing tool body thus holding the element frictionally in the body against the backing afforded by the usual conical expanding cam.

The primary object is to achieve greater honing accuracy than has been possible heretofore with elements of the above character through a more effective backing of the abrasive sticks of individual honing elements.

Another object is to incorporate in the molded casing of the honing element of the above character a bar of rigid non-resilient material which lies in direct contact with the expanding cone and with the bottom of the abrasive stick substantially through the length of the latter.

The invention also resides in the novel manner of locking the backing bar to the end blocks of the plastic casing.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in

which FIGURE 1 is a fragmentary longitudinal section of a honing tool having honing elements embodying the novel features of the invention, the section being taken along the line 1-1 of FIG. 2.

FIG. 2 is a cross-section taken along the line 2-2 of FIG. l.

FIG. 3 is an enlarged fragmentary section of part of FIG. 2.

FIG. 4 is a perspective View of the improved honing element.

FIG. 5 is an exploded perspective view of the abrasive stick and its supporting bar.

FIG. 6 is a horizontal cross-section of the mold used in encasing the abrasive stick, the section being taken along line 6 6 of FIG. 7.

FIG. 7 is a fragmentary section taken along the line 7-'7 of FIG. 6.

FIG. 8 is a perspective view of a modiied form of the improved honing element.

FIGS. 9 and l0 are sections taken respectively along the lines 9 9 and 11B-10 of FIG. 8.

FIG. 11 is a longitudinal section taken along the line 11-11 of FIG. 9.

FIG. l2 is a similar section taken along the line 12-12 of FIG. 10.

FIG. 13 is a plan view of the mold and abrasive stick assembly as used in forming the element shown in FIG. 8.

FIGS. 14 and 15 are views similar to FIG. 9 showing modified forms of the bar for backing the honing stick.

FIG. 16 is a perspective view of the backing bar shown in FIG. l5.

The improved honing element in the forms shown in the drawings for purposes of illustration comprises an elongated bar or so-called stick 11 of bonded abrasive having square ends 11EL and uniform rectangular cross-section molded into and thus secured to a casing or shell 12 lCe composed of non-metallic material which will wear away with the working surface 18 of the stick during use of the element in a honing operation. The opposite side surfaces 14 of the shell are flat and merge with the rounded or semi-circular ends 15 of blocks 27 which abut with and project beyond the ends 11a of the stick so as to provide a snug friction it in correspondingly shaped radial slots 16 in a tubular carrier or body 17 of a honing tool. Such tools usually incorporate a conical expanding cam 20 disposed in direct line contact with the inclined bottom surface 19 of the honing element. The cam is formed on the end of a rod 21 slidable endwise in the body 17 in one direction to expand the honing elements into engagement with the work bore under the desired honing pressure and in the opposite direction to free the elements and permit collapse of the hone. Among the plastic materials having the desired wearing characteristics are general purpose phenolic resins such as Durez 791. Such materials possess some degree of compressibility which enables the shell to be held frictionally in the body slot 17. By rounding the ends 15 of the plastic shell, the latter are adapted to fit with the desired snugness in the ends of the body slots 17 which ends are preferably formd in drilling operations.

In accordance with the present invention, a bar 23 of non-resilient non-compressible material, preferably metal, which is molded into the shell beneath the stick 11, defines the bottom surface 19 for contacting the expanding cam 20 and has a flat upper surface 24 lying in full face to face contact with the bottom surface 25 of the abrasive stick substantially the full length and over a substantial part of the width of this surface. As a result, the stick is backed solidly and rigidly along its full length so that the entire pressure on the working face 18 during a honing operation is transmitted downwardly to the expanding cam through the non-compressible backing. By thus preventing any yielding of the support for the stick, the working face is held at all times precisely in the radial position determined by the expanding cam. It has been found in practice that the dimensional accuracy of the bores honed by the present tool may be increased substantially through the use of such rigid backings.

In plastic mounted honing elements of the present type, one or both sides of the stick may be covered by a thin layer 22 of the plastic which preferably is made only thick enough to hold the abrasive surfaces properly out of rubbing contact with the side walls of the slots 16 in the tool body. Also, in order to hold the abrasive stick and the backing bar properly centered during the molding operation later described, the walls 22 are left interrupted by grooves 34. Therefore, the plastic walls 22 cannot be relied on to secure the parts together throughout the service life of the element during which the walls 22 Wear away with the abrasive.

To effect the desired secure fastening, the upper end portions of the blocks 27 are secured to the ends 11a of the stick 11 and the lower end portions are interlocked mechanically with the sides of the backing bar 23. The attachment to the stick ends is achieved by virtue of the flow of the molten plastic during the molding operation into the open pores of the abrasive at the ends 1184 thus etfectually locking the latter to the blocks. The mechanical fastening is achieved by molding the lower end portions of the block integral with the outer ends of members 26 which extend along the sides of the bar 23 and are formed in the molding operation by the ow of molten plastic into recesses formed along side surfaces 26a of the bar below the top surface 24 thereof and spaced inwardly from the planes a of the opposite sides of the stick far enough to impart the required lateral thickness and therefore strength to the locking members 26.

FDhe side recesses may vary in number and cross-sectional shape while properly holding the molded assembly together as the abrasive stick wears away in service use. In the forms shown in FIGS. l through 12, the recesses .take the form of channels extending along opposite sides of the bar -the full length thereof and detined by substantially right angular flanges 2S and 29 projecting equal distances outwardly from the upper and lower ends of a vertical connecting web 23a. Thus, the bar, as used in the molding operation, is of I-shaped cross-section which can be formed economically by extrusion through a die of the proper shape. Aluminum alloys such as are commonly used `for extrusion have been found satisfactory, althrough various other metals may be used.

To provide the desired rigid backing for the honing stick, the flat top sunface of the bar `23, formed by .the oppositely projecting llanges 23 extends along and contacts substantially the full length of the bottom surface 25 of the abrasive stick and across a substantial part of the width of the Istick bottom in each of the forms shown. In FIGS. 3 and 9, the bar `contacts the stick bottom across the full width of the latter thus imparting optimum backing rigidity. Preferably the Hanges 29 are of the same width as the lia'nges 28 because they are employed for the purpose of facilitating location of the bar 23 in proper relation with respect to the stick during the molding of the plastic shell 12. After the molding, part or all of these flanges 29 are cut away during milling of the assembly to form the bottom 19 at an angle corresponding to the cone angle of the expanding cam `2t) with ywhich the element is to be used. `In this oper-ation, the flange 29 may be cut away I along its full length as shown at the left in FIG. 1, or along only part thereof as shown in FIG. 12 le-aving some of the iange at one end of the element. Thus, the bar at the shallow end of the finished honing element may be T- shaped in cross-section while being of T or I shape at the large end depending on how much `of the molded assembly is cut away in tapering the molded assembly to the desired depth.

The honing element with the abrasive stick and the backing bar `23) in full contact with each other and positioned and securely fastened together in a unitary assembly as above described is formed in the operation of molding the shell 1.2 from a suitable non-metallic material which will wear away with the abrasive during a honing operation. Preparatory to molding, the stick and the bar 23 are positioned in a mold 30 (FIGS. 6 and 7) having a cavity corresponding in cross-section to that of the shell 12. The bar 23 rests on the bottom 31 of the cavity and is centered longitudinally in the latter by upstanding parallel pins 32 which similarly locate the abrasive stick 11. Lateral centering of the `bar and the stick is eitected by pairs of spaced vertical ribs 33 which project inwardly from the side walls of the cavity and bear against opposite sides of the stick and the outer edges of both of the bar flanges 23, 29.

Upon injection int-o .the cavity, the molten plastic flows into and lls the pores in the uncovered side surfaces of the stick, the channels between the flanges 28, 29 to form the locking members 26, the recesses around the pins to form the end blocks 27, and the narrow gaps at the ends of the positioning ribs 33 thus leaving thin layers of plastic at the bottoms of the grooves 34, these layers remaining attached to the abrasive after removal thereof from the mold. Also, the pins 32 form parallel holes 35 in the blocks 27 at opposite ends of the shell, these holes being open at both ends. After solidilication of the plas-tic material and removal of lthe assembly from the mold, the bottom edge is milled off to form the bottom surf-ace 19 inclined at the desired angle and the end of the element beveled off as indicated at 36 Where necessary in order to avoid interference between the elements when used in a hone of small diameter.

For honing certain Work materials, it may be desirable to form the mounting so as to leave exposed or subs-tantially the side of the abrasive stick which faces in the direction of rotation of the tool in service use while providing the same rigid backing for the stick by mounting the bar 23 in the same relation with respect to the stick bottom. Such a construction is illustra-ted in FIGS. 8 through 13 in which the abrasive stick and the bar 23 are shifted laterally in the mold cavity against against one wall thereof and held in this position during the molding by ribs 33 projecting from the opposite vwall of the cavity, the stick and bar being positioned endwise as before by pins 32.

With this arrangement, the plastic shell is molded t0 the cross-section shown in FIG. 9 in which one face of the abrasive stick and one edge of a flange 28 remain ex- Iposed on the side of the element which is to become the leading face in service operation. Then, when .the lower edge portion of the assembly as removed from the mold and shown -in FIGS. 9 and 1l is milled to form the inclined bottom 19, part or all of the flanges 29 may be cut ott` as shown in FIGS. l1 and l2 to leave the crosssection shown in FIG. 10. The lower remaining edge 40 of the web 22:2l is however positioned to bear against the expanding cam 20 and transmit the honing pressure directly from the stick to the cam.

In the form of the invention shown in FIG. 14, the recesses 26b in the sides of the backing bar are multiplied and made smaller in cross-section so as to form a series of the locking members 26c vertically spaced along and combining to impart the desired over-all strength to the members 26 that lock the lower end portions of the blocks 27 to the bar 23. The latter need not extend laterally the Vfull width of the bottom surface of the abrasive stick in order to back the abrasive stick with the desired rigidity. When such a backing bar narrower than the bottom of the abrasive stick is used, proper provision is made in the construction of the mold cavity to locate the bar before the molding operation in proper position relative to the bottom of the abrasive stick.

For certain honing installations, the desired rigid backing of the stick may be achieved with a bar 23 of still narrower width but still having a top surface 24 contacting the bottom of the stick substantially throughout the length of the latter. Such a modification is shown in FIGS. l5 and 16 in which the bar 23 is a stamping comprising a relatively flat and thick plate 41 substantially equal in =length to the abrasive stick 11. and extending along the llongitudinal center Iline of the bottom 2.5 of the stick. Feet i2 spaced along and struck out of the metal of the bar serve to support the bar in the mold cavity preparatory to injecting the molten plastic. The members 25 formed below the abrasive stick in the molding operation are somewhat wider and stronger than in the yforms shown in FIGS. 3, 9 and 14 and such a construction may be employed where `the rigid backing need not .be extended over the full width of the stick bottom. If desired, the locking members 26 may be joined integrally by the -ow of the plastic through holes 43 spaced along the plate 41.

It will be apparent that the constructions above described provide for adequate and rigid backing of the abrasive stick and for the transmission of the working pressure from the stick directly to the expanding cam along substantially the full length of the bottom surface of the stick. The working face 18 is thus maintained at all times in a precise radial position determined by the axial position of the expanding cam 20. High precision in honing the work bore to a desired size is thus achieved. At the same time, the parts of the hon-ing element may be joined together in a simple plastic molding operation and effectulally maintained in this relation throughout the service life of the element which involves a gradual wearing down of the abrasive stick and the backing layer 22 of the plastic shell.

The holes 35 left by the pins and extending beyond the full depth of the abrasive are used to perform the new function of facilitating removal of the worn out elements from the tool body. This may be accomplished by the use of a pincher type tool similar to that used in removing ordinary snap rings and having pin-like projections sized to lit loosely into the holes 35. After insertion in the holes, the projections are urged laterally toward each other by squeezing of the tool handles thus gripping the shell 12 so that the honing element may be lifted easily out of the body recess i6 even after the full depth of the `abrasive stick has been worn away.

This application is a oontinuation-in-part of our coprend- -ing application Serial No. 55,028, filed September 9, 1960, now abandoned.

We claim as our invention:

1. A honing element having, in combination, a generally rectangular stick of bonded abrasive, a solid bar of rigid non-resilient material such as metal underlying said stick and having a fiat top surface lying in direct Contact With the bottom of the stick over substantially the full length and Width thereof, said bar having a channel extending along at least one side substantially throughout the length of the bar, and a casing molded around the sides and ends of said stick and said bar and filling said channel to thereby lock said stick and bar together with the working face of said stick and the bottom of said bar exposed, said casing being composed of material such as plastic which will Wear away with said working face in a honing operation.

2. A honing element having, in combination, a generally rectangular stick of bonded abrasive, a solid bar of rigid non-resilient material such as metal underlying said stick and having a flange projecting laterally from and extending along the top edge of the bar and cooperating with the latter to define a fiat top surface lying in direct contact with the bottom of the stick over substantially the full length and Width thereof, said flange and the side of the bar forming a channel extending along substantially the full length of the bar, and a casing of molded plastic material extending around the sides and ends of said bar and the ends and one side of the stick and filling said channel to thereby lock said stick, said bar and the ends of said casing together in a rigid assembly with the working face of said stick and the bottom of said bar exposed.

3. A honing element having, in combination, a generally rectangular stick of bonded abrasive, a bar of rigid non-resilient material such as metal of T-shaped crosssection underlying said stick and having a fiat top surface formed by the cross-piece of the T and lying in full direct contact with the bottom of the stick over substantially the full length and a substantial part of the width thereof, and a molded casing extending around the sides and ends of said bar and the ends of said stick to unite said stick, said bar and the casing together in a solid assembly of rectangular cross-section with the working face of said stick and the bottom of said bar exposed and the ends of the casing beyond the stick integrally joined by the portion of said casing filling opposite sides of the T, said casing being composed of material such as plastic which will wear away with said working face in a honing operation.

4. A honing element as defined in claim 3 in which said bar in the initial molded assembly is of I-shaped crosssection.

5. A honing element comprising an elongated squareended stick of bonded abrasive and of rectangular crosssection, an elongated rigid backing for said stick comprising a bar of non-compressible material such as metal and of a length substantially equal to that of said stick and having a flat top surface lying against and in direct face to face contact with the bottom surface of the stick substantially throughout the length thereof, at least a portion of each of the opposite side surfaces of said bar along the end portions thereof being spaced inwardly from the planes of the opposite side surfaces of said stick, and a casing of plastic material molded around said stick and said bar to join the same into a unitary assembly with the plastic entering the pores of the abrasive at the ends of said stick, said casing comprising blocks enclosing opposite ends of said stick and bar and presenting rounded surfaces facing outwardly in opposite directions from such ends, and locking members extending along said side surfaces of said bar and integrally joined at their ends to said end blocks below the stick so as to lockthe blocks to the bar with the bottom thereof exposed whereby the honing pressure applied to the exposed top surface of said stick will be transmitted by said bar directly to the part supporting the honing element in service use.

6. A honing element as defined by claim 5 in which the portion of said backing bar adjacent the bottom of said stick is T-shaped in cross-section.

7. A honing element as defined by claim 5 in which at least a portion of said backing bar is I-shaped in crosssection.

8. A honing element comprising an elongated squareended stick of bonded abrasive and of rectangular crosssection, an elongated rigid backing for said stick comprising a bar of non-compressible material such as metal of a length substantially equal to that of said stick and having a flat top surface lying against and in direct face to face contact with the bottom surface of the stick substantially throughout the length thereof, at least a portion of one side surface of said bar along the full length thereof being spaced inwardly from the plane of the corresponding side surface of said stick, and a casing of plastic material molded around said stick and said bar to joint the same in a unitary assembly with the plastic entering the pores of the abrasive at the ends of said stick, said casing comprising blocks enclosing opposite ends of said stick and bar and presenting rounded surfaces facing outwardly in opposite directions from such ends, and a locking member extending along the recessed side of said bar and integrally joined at its ends to said end blocks below the stick so as to lock the blocks to the bar with the bottom thereof exposed whereby the honing pressure applied to the exposed top surface of said stick will be transmitted by said bar directly to the part supporting the honing element in service use.

9. A honing element having, in combination, a generally rectangular stick of bonded abrasive, a bar of rigid non-resilient material such as metal underlying said stick and having a flat top surface lying in contact with the bottom of the stick, and a casing of molded plastic material extending around the sides of said bar and at least the ends' of said stick and locking said stick and bar together with the Working face of said stick and the bottom of said bar exposed, the ends of said casing beyond the ends of said stick having parallel holes therein opening upwardly and extending into the plastic substantially down to the stick bottom and adapted to receive the prongs of a tool for lifting the element out of a hone body.

References Cited in the file of this patent UNITED STATES PATENTS 2,675,654 Harris Apr. 20, 1954 2,751,726 Klein June 26, 1956 2,952,952 Stanhope Sept. 20, 1960 

1. A HONING ELEMENT HAVING, IN COMBINATION, A GENERALLY RECTANGULAR STICK OF BONDED ABRASIVE, A SOLID BAR OF RIGID NON-RESILIENT MATERIAL SUCH AS METAL UNDERLYING SAID STICK AND HAVING A FLAT TOP SURFACE LYING IN DIRECT CONTACT WITH THE BOTTOM OF THE STICK OVER SUBSTANTIALLY THE FULL LENGTH AND WIDTH THEREOF, SAID BAR HAVING A CHANNEL EXTENDING ALONG AT LEAST ONE SIDE SUBSTANTIALLY THROUGHOUT THE LENGTH OF THE BAR, AND A CASING MOLDED AROUND THE SIDES AND ENDS OF SAID STICK AND SAID BAR AND FILLING SAID CHANNEL TO THEREBY LOCK SAID STICK AND BAR TOGETHER WITH THE WORKING FACE OF SAID STICK AND THE BOTTOM OF SAID BAR EXPOSED, SAID CASING BEING COMPOSED OF MATERIAL SUCH AS PLASTIC WHICH WILL WEAR AWAY WITH SAID WORKING FACE IN A HONING OPERATION. 